ESTIMATING LEAKS IN WATER DISTRIBUTION SYSTEMS BY SEQUENTIAL STATISTICAL ANALYSIS OF CONTINUOUS FLOW READINGS

 
 
 
 

ESTIMATING LEAKS IN WATER DISTRIBUTION SYSTEMS BY SEQUENTIAL STATISTICAL ANALYSIS OF CONTINUOUS FLOW READINGS

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Title: ESTIMATING LEAKS IN WATER DISTRIBUTION SYSTEMS BY SEQUENTIAL STATISTICAL ANALYSIS OF CONTINUOUS FLOW READINGS
Author: NADIMPALLI, GAYATRI
Description: Leakage in water distribution pipes is a major problem faced by the water industry. Water utilities often employ traditional audit methods to estimate water lost as leakage. Many hydraulic models have also been developed in the recent past to estimate leakage rates and locate leaks. However, water audits give an approximate estimate of the leakage rates and the mathematical models can be applied under certain hydraulic conditions only. In this thesis, a new method is presented for detecting the magnitude of leaks in residential service zones of a drinking water distribution system. It is assumed that continuous measurements of flow rates through the main supply line into a residential service zone are available during periods of low use. The procedure involves computing the sample mean and variance from the set of measured flow rates as these flows are truncated progressively from below. Trajectories of the sample statistics and their derivatives are plotted versus the level of data truncation. In the presence of leaks, these trajectories diverge from their expected theoretical path when plotted on a standardized graph derived from a mixed truncated normal distribution. The point of departure on the standardized graph indicates where the truncation threshold matches the maximum rate of network leakage. A performance limit for the proposed method is derived to account for spatial constraints reflecting network size and time constraints arising from interval averaging. A simple example is presented first where the leakage is assumed to be of constant magnitude. The leak analysis is then extended to a more complicated case where pressure fluctuations in the distribution system add a statistical noise to the flow measurements. Results show that the method developed in this thesis estimates leakage rates quite accurately even in the presence of statistical noise. The method can be used to estimate leakage rates in branching mainlines or residential District Metering Areas (DMAs) where flows can be measured continuously for a sufficiently long period of time.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1068674771
http://hdl.handle.net/2374.OX/11210
Date: 2003

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